Sufficient quality between a base station and a mobile user may usually be achieved by increasing a transmission power. However, higher power may increase an overall noise level, which may effectively reduce system capacity, per base station coverage and throughput. Service time of mobile units may also be reduced due to higher battery drain.
Transmit diversity may provide multiple solutions by transmission from more than one antenna, particularly at a mobile communication device. Transmission from multiple antennas may be selective where only one antenna may be active at any time, or may be combined, with a simultaneous transmission from multiple antennas. In order for transmit diversity to be effective, transmission from multiple antennas may require control of parameters of signals that may be fed to these antennas, and may be designated diversity parameters. This control may depend on a type of transmit diversity that may be applied.
Some solutions that may control transmit diversity may include a diversity control that may be based on a channel modeling. This channel modeling may be based on feedback that may be provided by a receiving end, or an estimation of a transmission channel at the transmitting device, from reception of an opposite channel. Other solutions may be by blind diversity control, such as Space Time Coding (STC). Other solutions may be by a power control feedback based transmit diversity.
These solutions may have drawbacks, which may include requiring changes to an air interface standard, as is the case for STC, or performance limitations.